Curable organopolysiloxane composition and a semiconductor device made with the use of this composition

ABSTRACT

A curable organopolysiloxane composition includes: (A) a straight-chain organopolysiloxane having per molecule at least two silicon-bonded alkenyl groups and at least one silicon-bonded aryl group; (B) a branched-chain organopolysiloxane with siloxane units represented by the following general formula: RSiO 3/2 , where R is a substituted or unsubstituted monovalent hydrocarbon group, and having per molecule at least one silicon-bonded alkenyl group and at least one silicon-bonded aryl group; (C) an organopolysiloxane having in one molecule at least two silicon-bonded hydrogen atoms; and (D) a hydrosilylation catalyst; and a semiconductor device with a semiconductor element coated with a cured body of the aforementioned composition.

TECHNICAL FIELD

This invention relates to a curable organopolysiloxane composition and asemiconductor device using this composition. More specifically, theinvention relates to a curable organopolysiloxane composition suitablefor forming a cured object with a high coefficient of refraction, a highcoefficient of light penetration, improved strength, and improvedresistance to scratching. The invention also relates specifically to asemiconductor device, which possesses high reliability and is coveredwith the aforementioned cured object.

BACKGROUND ART

Curable organopolysiloxane compositions and curable epoxy resincompositions are used as protective, coating, and sealing agents forsemiconductor elements of such semiconductor devices as photocouplers,light-emitting diodes, solid-state imaging devices, etc. It is requiredthat such curable organopolysiloxane compositions and curable epoxyresin compositions neither absorb nor scatter the light emitted orreceived from a semiconductor element. Furthermore, a cured objectproduced from these compositions should possess high strength andresistance to scratching.

A cured object obtained from a known curable organopolysiloxanecomposition comprising an organopolysiloxane with at least twosilicon-bonded alkenyl groups per molecule, an organopolysiloxane withat least two silicon-bonded hydrogen atoms, and a hydrosilylationcatalyst is characterized by low mechanical strength and low resistanceto scratching. As far as the is concerned, with the lapse of time, anobject obtained by curing the curable epoxy resin composition changesits color and becomes less permeable to light. This leads to decrease inreliability of semiconductor devices produced with the use of such acomposition.

It is an object of this invention to provide a curableorganopolysiloxane composition suitable for forming a cured objectcharacterized by a high coefficient of refraction, excellent lightpermeability, high mechanical strength and resistance to scratching. Itis a further object to provide a highly reliable semiconductor devicecovered with the aforementioned cured object.

DISCLOSURE OF INVENTION

This invention provides a curable organopolysiloxane compositioncomprising:

(A) a straight-chain organopolysiloxane having per molecule at least twosilicon-bonded alkenyl groups and at least one silicon-bonded arylgroup;

(B) a branched-chain organopolysiloxane having siloxane unitsrepresented by the following general formulaRSiO_(3/2)where R is a substituted or unsubstituted monovalent hydrocarbon group,and where componet (B) has per molecule at least one silicon-bondedalkenyl group and at least one silicon-bonded aryl group; and wherecomponent (B) is used in a weight ratio of 1/99 to 99/1 based on theweight of component (A);

(C) an organopolysiloxane having per molecule at least twosilicon-bonded hydrogen atoms; where component (C) is used in an amountof 1 to 200 parts by weight for each 100 parts by weight of total weightof parts (A) and (B); and

(D) a hydrosilylation catalyst in an amount sufficient to promote curingof the composition.

The invention further provides a semiconductor device covered with anobject obtained by curing the curable organopolysiloxane composition.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a photocoupler as an example of asemiconductor device of the invention.

FIG. 2 is a cross-sectional view of a LED as an example of asemiconductor device of the invention.

REFERENCE NUMERALS

-   -   1 semiconductor element    -   2 lead frame    -   3 bonding wire    -   4 semiconductor element    -   5 lead frame    -   6 bonding wire    -   7 cured body produced from the curable organopolysiloxane    -   8 sealing resin    -   9 semiconductor element    -   10 lead frame    -   11 lead frame    -   12 bonding wire    -   13 cured body produced from the curable organopolysiloxane        composition    -   14 transparent sealing resin

DETAILED DESCRIPTION OF THE INVENTION

Component (A) comprises a straight-chain organopolysiloxane having permolecule at least two silicon-bonded alkenyl groups and at least onesilicon-bonded aryl group. Alkenyl groups contained in component (A) canbe represented by vinyl groups, allyl groups, butenyl groups, pentenylgroups, and hexenyl groups. The most preferable are vinyl groups. Arylgroups contained in component (A) can be represented by phenyl groups,tolyl groups, xylyl groups, and naphthyl groups. The most preferable arephenyl groups. Organic groups, other than alkenyl and aryl groups thatare silicon-bonded and can be used in component (A) may comprise thefollowing substituted or unsubstituted monovalent hydrocarbon groups:methyl groups, ethyl groups, propyl groups, butyl groups, pentyl groups,hexyl groups, heptyl groups, or similar alkyl groups; benzyl groups,phenethyl groups, or similar aralkyl groups; chloromethyl groups,3-chloropropyl groups, 3,3,3-trifluoropropyl groups, or similarhalogenated alkyl groups. Among these, most preferable are methylgroups. To reduce damping of light under the effect of such phenomena asdiffraction, reflection, scattering, etc., that may occur in a curedobject obtained from the composition of the invention, it is recommendedthat the amount of silicon-bonded aryl groups among the silicon-bondedorganic groups contained in component (A) be not less than 40 mole %,preferably not less than 45 mole %. Although there are no specialrestrictions with regard to viscosity of component (A) at 25° C., it isrecommended that the viscosity be 10 to 1,000,000 mPa·s, preferably 100to 50,000 mPa·s. This is because the viscosity of component (A) belowthe recommended lower limit will decrease mechanical strength of thecured object, while the viscosity above the recommended upper limit willmake the composition more difficult to handle.

The organopolysiloxane of component (A) has a straight-chain molecularstructure and is expressed by the following general formula:

where each R¹ may be the same or different and may comprise substitutedor unsubstituted monovalent hydrocarbon groups, such as theaforementioned alkyl groups, alkenyl groups, aralkyl groups, andhalogenated alkyl groups. Per molecule of this component, at least twoR¹'s must be alkenyl groups, and at least one of R¹ must be an arylgroup. In the above formula, n is an integer of 5 to 1000.

Component (B) imparts mechanical strength and high resistance toscratching to an object obtained by curing the composition of theinvention. Component (B) is a branched-chain organopolysiloxane withsiloxane units represented by the following general formula:RSiO_(3/2)Alkenyl groups contained in component (B) are the same as those definedabove. The most preferable are vinyl groups. Aryl groups used incomponent (B) are also the same as defined above with phenyl groupsbeing preferable. Furthermore, in component (B), silicon-bonded organicgroups other than alkenyl groups may comprise the aforementioned alkylgroups, aralkyl groups, halogenated alkyl groups or similar substitutedor unsubstituted monovalent hydrocarbon groups. Among these, methylgroups are preferable. R is a substituted or unsubstituted monovalenthydrocarbon group that can be represented by the aforementioned alkylgroups, alkenyl groups, aryl groups, aralkyl groups, and halogenatedalkyl groups. Most preferable for R are alkyl and aryl groups, and amongthese, the methyl and phenyl groups.

The organopolysiloxane can be represented by the following average unitformula:(R²SiO_(3/2))_(a)(R² ₂SiO_(2/2))_(b)(R² ₃SiO_(1/2))_(c)(SiO_(4/2))_(d)(XO_(1/2))_(e),where each R² may be the same or different substituted or unsubstitutedmonovalent hydrocarbon groups, such as the aforementioned alkyl groups,alkenyl groups, aryl groups, aralkyl groups, and halogenated alkylgroups. It is recommended that 0.1 to 40 mole % of all R²'s are alkenylgroups. This is because with the amount of alkenyl groups below therecommended lower limit, component (B) will have low reactivity withrespect to component (C). An increase in the amount of alkenyl groupsbeyond the recommended upper limit will also reduce reactivity tocomponent (C). To reduce the loss of light passing through the curedbody of the composition due to refraction, reflection, scattering, etc.,it is recommended that more than 10 mole % of all R²'s be theaforementioned aryl groups and preferably phenyl groups. Furthermore, itis recommended that more than 30 mole % of the R²'s contained in theR²SiO_(3/2) siloxane units of component (C) comprise aryl groups andpreferably phenyl groups. In the above formula, groups other thanalkenyl groups for R² are methyl groups. X may designate a hydrogen atomor alkyl group. Examples of the alkyl groups are the same as givenabove. The most preferable are methyl groups. Furthermore, in the aboveformula, a is a positive number, b is 0 or a positive number, c is 0 ora positive number, d is 0 or a positive number, e is 0 or a positivenumber, b/a is 0 to 10, c/a is 0 to 0.5, d/(a+b+c+d) is 0 to 0.3, ande/(a+b+c+d) is 0 to 0.4. Although there are no special restrictions withregard to the molecular weight of component (B), it is recommended tohave a weight-average molecular weight (M_(w)) of this component(recalculated to the reference polystyrene) is 500 to 10,000, preferably700 to 3,000.

In the composition of the invention, component (B) is used in a weightratio of 1/99 to 99/1, preferably 10/90 to 90/10, and even morepreferably, 20/80 to 80/20 to the weight of component (A). If component(B) is used in an amount below the recommended lower limit, a curedobject will have a reduced mechanical strength and resistance toscratching. If the amount of component (B) exceeds the recommended upperlimit, it would be either difficult to handle the composition, or theobtained cured body will have an extremely high hardness.

Component (C) is a curing agent of the composition. Component (C) is anorganopolysiloxane having at least two silicon-bonded hydrogen atoms inone molecule. The organic silicon-bonded groups of component (C) can berepresented by the aforementioned alkyl groups, aryl groups, aralkylgroups, halogenated alkyl groups and similar substituted orunsubstituted monovalent hydrocarbon groups, except for alkenyl groups.Among these, preferable are alkyl and aryl groups, especially methyl andphenyl groups. There are no special restrictions about the state ofcomponent (C), but preferably it should be in a liquid or solid state at25° C. Most preferable state is a liquid with the viscosity of 0.1 to1,000,000,000 mPa·s at 25° C.

The molecular structure of component (C) may be straight,partially-branched straight, branched, or net-like. To impart bettermechanical strength and resistance to scratching to a cured object, thebranched structure is preferable. Such a branched organopolysiloxane isrepresented by the following average unit formula:(R³SiO_(3/2))_(f)(R³ ₂SiO_(2/2))_(g)(R³ ₃SiO_(1/2))_(h)(SiO_(4/2))_(i)(X′O_(1/2))_(j),where each R³ may be the same or different and may comprise hydrogenatoms or substituted or unsubstituted monovalent hydrocarbon groups,except for alkenyl groups. Examples of such monovalent hydrocarbongroups are the aforementioned alkyl groups, aryl groups, aralkyl groups,and halogenated alkyl groups. It is preferable to have silicon-bondedhydrogen atoms in an amount of 0.1 to 40 mole % of all R³ 's. If thecontent of silicon-bonded hydrogen atoms is below the recommended lowerlimit, the composition will be difficult to cure. If the recommendedupper limit is exceeded, a cured object will have a reduced thermalresistance. To reduce the loss of light passing through the cured bodyof the composition due to refraction, reflection, scattering, etc., itis recommended that 10 mole % or more of all R³'s be the aforementionedaryl groups and preferably phenyl groups. Furthermore, it is recommendedthat 30 mole % or more of the R²'s contained in the R³SiO_(3/2) siloxaneunits of component (C) comprise aryl groups and preferably phenylgroups. In the above formula, groups other than aryl groups and hydrogenatoms that may contain R³'s are methyl groups; X′ may designate ahydrogen atom or alkyl groups. Examples of the alkyl groups are the sameas given above. The most preferable are methyl groups. Furthermore, inthe above formula, f is a positive number, g is 0 or a positive number,h is 0 or a positive number, i is 0 or a positive number, j is 0 or apositive number, g/f is 0 to 10, h/f is 0 to 0.5, i/(f+g+h+i) is 0 to0.3, and j/(f+g+h+i) is 0 to 0.4. Although there are no specialrestrictions with regard to the molecular weight of component (C), it isrecommended to have a weight-average molecular weight (Mw) of thiscomponent (recalculated to the reference polystyrene) within the rangeof 300 to 10,000, preferably 500 to 3,000.

Component (C) is used in an amount of 1 to 200 parts by weight for each100 parts by weight of the sum of components (A) and (B). If the amountof component (C) is below the recommended lower limit, it will bedifficult to provide sufficient curing of the composition. If component(C) is used in an amount exceeding the recommended upper limit, thecured product will have insufficient thermal resistance. For the abovereasons, it is recommended that the silicon-bonded hydrogen atoms in thecomponent (C) are preferably within a range of 0.1 to 10 moles, morepreferably within a range of 0.1 to 5 moles, and even more preferablywithin a range of 0.5 to 5 moles, per 1 mole of the sum of alkenylgroups contained in components (A) and (B).

Component (D) is catalyst for a hydrosilylation reaction between alkenylgroups of components (A) and (B) and silicon-bonded hydrogen atoms ofcomponent (C). In other words, component (D) is a hydrosilylationcatalyst that accelerates curing of the composition. Examples ofcomponent (D) are platinum-type catalysts, rhodium-type catalysts, andpalladium-type catalysts, of which platinum-type catalysts are mostpreferable. The following are examples of the platinum catalyst suitablefor the invention: platinum fine powder, chloroplatinic acid, alcoholicsolution of the chloroplatinic acid, a platinum-alkenylsiloxane complex,platinum-olefin complex, platinum-carbonyl complex. The most preferableis the platinum-alkenylsiloxane complex. The alkenylsiloxane can berepresented by the following compounds:1,3-divinyl-1,1,3,3-tetramethyldisiloxane,1,3,5,7-tetramethyl-1,3,5,7-tetravinyl cyclotetrasiloxane,alkenylsiloxane having a part of methyl groups of the alkenylsiloxanesubstituted by ethyl groups, phenyl groups or the like, andalkenylsiloxane having vinyl groups of the alkenylsiloxane substitutedby allyl groups, hexenyl groups, or the like. Among these, the mostpreferable is 1,3-divinyl-1,1,3,3-tetramethyldisiloxane that impartshigh stability to the platinum-alkenylsiloxane complex. For furtherimprovement in the stability of the platinum-alkenylsiloxane complexes,it is recommended to combine the aforementioned complexes withorganosiloxane oligomers such as1,3-divinyl-1,1,3,3-tetramethyldisiloxane,1,3-diallyl-1,1,3,3-tetramethyldisiloxane,1,3-divinyl-1,3-dimethyl-1,3-diphenyldisiloxane,1,3-divinyl-1,1,3,3-tetraphenyldisiloxane, or1,3,5,7-tetramethyl-1,3,5,7-tetravinyl cyclotetrasiloxane, or a similaralkenylsiloxane or methylsiloxane oligomer. The most preferable for theaddition is alkenylsiloxane.

There are no special limitations with regard to the amount of component(D) required for acceleration of curing of the composition. The mostpreferable amount provides a content of metal atoms contained (in weightunits) in component (D) of 0.01 to 1,000 ppm. If component (D) iscontained in an amount below the recommended lower limit, it would bedifficult to ensure sufficient curing, while with the amount ofcomponent (D) exceeding the recommended upper limit, there may beproblems associated with coloration of the cured object.

If necessary, the composition may be combined with other optionalcomponents such as 2-methyl-3-butyn-2-ol, 3,5-dimethyl-1-hexyn-3-ol,2-phenyl-3-butyn-2-ol, or similar alkynyl alcohols;3-methyl-3-penten-1-yne, 3,5-dimethyl-3-hexen-1-yne, or a similar enynecompound; 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane,1,3,5,7-tetramethyl-1,3,5,7-tetrahexenylcyclotetrasiloxane,benzotriazole, or a similar hydrosilylation reaction inhibitor. Althoughthere are no special restriction with regard to the amount of theaforementioned reaction inhibitors added to the composition, it isrecommended to use these inhibitors in an amount of 0.0001 to 5 parts byweight for each 100 parts by weight of the sum of the amounts ofcomponents (A) and (B).

If necessary, an adhesion-imparting agent can be added to thecomposition of the invention for improving its adhesive properties. Suchan agent may comprise an organic silicon compound which is differentfrom aforementioned components (A), (B), and (C) and which contains atleast one silicon-bonded alkoxy group per molecule. This alkoxy groupcan be represented by a methoxy group, ethoxy group, propoxy group,butoxy group, and a methoxyethoxy group. A methoxy group is the mostpreferable. Groups other than the aforementioned silicon-bonded alkoxygroups of the organic silicon compound also can be used. Examples ofsuch other groups are the following: substituted or unsubstitutedmonovalent hydrocarbon groups such as the aforementioned alkyl groups,alkenyl groups, aryl groups, aralkyl groups; 3-glycidoxypropyl groups,4-glycidoxybutyl groups, or similar glycidoxyalkyl groups;2-(3,4-epoxycyclohexyl) ethyl groups, 3-(3,4-epoxycyclohexyl) propylgroups, or similar epoxycyclohexyl groups; 4-oxiranylbutyl groups,8-oxiranyloctyl groups, or similar oxiranylalkyl groups, or otherepoxy-containing monovalent organic groups; 3-methacryloxypropyl groups,or similar acryl-containing monovalent organic groups; and hydrogenatoms. At least one of these groups can be contained in one molecule.The most preferable are epoxy-containing and acryl-containing monovalentorganic groups. It is recommended that the aforementioned organicsilicon compounds contain groups to react with components (A) and (B),or (C), in particular such groups as silicon-bonded alkenyl groups andsilicon-bonded hydrogen atoms. For better adhesion to various materials,it is preferable to use the aforementioned organic silicon compoundsthat have at least one epoxy-containing monovalent group per molecule.Examples of such compounds are organosilane compounds and organosiloxaneoligomers. The aforementioned organosilane oligomers may have astraight-chain, partially-branched straight-chain, branched-chain,cyclic, and net-like molecular structure. The straight-chain,branched-chain, and net-like structures are preferable. The followingare examples of the aforementioned organic silicon compounds:3-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, or similarsilane compounds; a siloxane compound having in one molecule at leastone silicon-bonded alkenyl group, or at least one silicon-bondedhydrogen atom, or at least one silicon-bonded alkoxy group, a silanecompound having at least one silicon-bonded alkoxy group, a mixture of asilane or a siloxane compound having at least one silicon-bonded alkoxygroup with a siloxane compound having in one molecule at least onesilicon-bonded hydroxyl group and at least one silicon-bonded alkenylgroup, a siloxane compound represented by the following formula:

where k, m, and p are positive numbers, and a siloxane represented bythe following formula:

where k, m, p, and q are positive numbers. It is recommended that theaforementioned adhesion-imparting agents be in a low-viscosity state.There are no special restrictions with regard to the value of theviscosity. However, it is recommended for viscosity to be 1 to 500 mPa·sat 25° C. Although there are no special restrictions with regard to thecontent of the adhesion-imparting agent in the composition, it isrecommended to use it in the amount of 0.01 to 10 parts by weight foreach 100 parts by weight of the sum of components (A) and (B).

If the composition of the invention is used as a protective agent for asemiconductor element of a light-emitting diode (LED), it may contain aluminescent substance, e.g., of a yttrium-aluminum-garnet system.Although there are no special restrictions with regard to the content ofthe luminescent substance, the recommended range is 1 to 20 wt. %,preferably, 5 to 15 wt. % of the total weight of the composition. Withinlimits not conflicting with the objects of the invention, thecomposition may further comprise other optional additives, such assilica, glass, alumina, zinc oxide, or similar inorganic fillers;polymethacrylate resin, or a similar organic resin in the form of a finepowder; heat-resistant agents, dyes, pigments, flame retarders,solvents, etc.

It is recommended that the index of refraction (at 25° C.) for visiblelight (589 nm) passing through the cured body obtained from thecomposition of the invention be not less than 1.5. It is alsorecommended that light permeability (at 25° C.) for the visible light(420 nm) passing through the cured body obtained from the composition ofthe invention, be not less than 80%. This is because it would bedifficult, with the index of refraction below 1.5 or with lightpermeability below 80%, to impart sufficient reliability to asemiconductor device that incorporates a semiconductor element coatedwith a cured body of the composition. To obtain a curableorganopolysiloxane composition suitable for forming a cured body withsuch high values of the index of refraction and light permeability, itis recommended that all components (A) to (C) have substantially thesame index of refraction. More specifically, it is recommended thatamong all organic groups component (A) contain 40 mole % or more,preferably 45 mole % or more of silicon-bonded aryl groups and thatsilicon-bonded organic groups other than the aforementioned aryl andalkenyl groups comprise alkyl groups, in particular methyl-containingorganopolysiloxanes. For the same purpose, it is recommended that amongall organic groups component (B) contain 10 mole % of silicon-bondedaryl groups and that silicon-bonded organic groups, other than theaforementioned aryl and alkenyl groups, comprise alkyl groups, inparticular methyl-containing organopolysiloxanes. For the same purpose,it is recommended that among all organic groups component (C) contain 10mole % of silicon-bonded aryl groups and that silicon-bonded organicgroups, other than the aforementioned aryl groups, comprise alkylgroups, in particular methyl-containing organopolysiloxanes. The indexof refraction can be measured, e.g., by the Abbe refractometer. In thiscase, indices of refraction can be measured at different wavelengths bychanging the wavelength of a light source used in the Abberefractometer. Furthermore, light permeability, e.g., for a cured bodywith optical path length of 1.0 mm, can be measured with the use of aspectrophotometer.

It is also recommended that at 25° C. permeability of ultraviolet (UV)rays with wavelengths of 200 nm to 250 nm through a cured body obtainedfrom the composition of the invention do not exceed 10%. This is becauseotherwise it would be impossible to protect the structural material ofthe semiconductor device that incorporates a semiconductor elementcoated with a cured body of the composition of the invention fromdeterioration under the effect of UV rays of a short wavelength in therange of 200 nm to 250 nm. UV light permeation can be measured, e.g., ina cured body with a 1.0 mm optical path, with the use of aspectrophotometer.

The composition of the invention can be cured at room temperature orwith heating. Curing with heating is recommended for acceleration of theprocess. The temperature recommended for curing with heating is 50 to200° C. A cured body obtained by curing the composition of the inventionmay have a rubber-like structure, in particular, the structure of hardrubber or a flexible resin. In the manufacture of electric andelectronic devices, the composition of the invention is suitable for useas an adhesive agent, bonding agent, protective agent, coating agent,sealing agent, and an underfill agent. In particular, the compositionsof the invention are most suitable as protective, coating, and sealingagents for use with semiconductor elements of optical semiconductordevices operating under conditions of high light permeation.

The following is a detailed description of a semiconductor device of theinvention. The device of the invention is characterized by having asemiconductor element coated with a cured body made from the curableorganopolysiloxane composition of the invention. The aforementionedsemiconductor element may comprise a diode, transistor, thyristor,solid-state image pickup element, as well as a semiconductor element ofa monolithic IC or a hybrid IC. Furthermore, the aforementionedsemiconductor device may comprise an optical semiconductor device, suchas a diode, a light-emitting diode (LED), transistor, thyristor,photocoupler, charge coupled device (CCD), monolithic IC, hybrid IC,LSI, and VLSI. Optical semiconductor devices most suitable forapplication of the invention are light-emitting diodes (LED's) andphotocouplers.

FIG. 1 is a cross-sectional view of a photocoupler shown as one exampleof the device of the invention, and FIG. 2 is a cross-sectional view ofa single LED used in the aforementioned device. The photocoupler shownin FIG. 1 contains a semiconductor element 1 formed by a compoundsemiconductor body and attached to a lead frame 2 by die-bonding and bya bonding wire 3 to another lead frame 2 not shown in the drawings. Alight-receiving semiconductor element 4 located opposite to thesemiconductor element 1 is die-bonded to a lead frame 5 and by a bondingwire 6 to another lead frame 5 not shown in the drawing. The spacebetween the semiconductor elements is filled with a transparent curedbody 7 of a curable organopolysiloxane composition of the invention.Furthermore, the semiconductor element covered by the cured body 7 issealed with the use of the sealing resin 8.

In the production of the photocoupler shown in FIG. 1, the semiconductorelement 1 is die-bonded to the lead frame 2, and then the semiconductorelement 1 and another separate lead frame 2 (which is not shown inFIG. 1) are wire-bonded with the use of a bonding wire 3 made of gold.In a similar manner, a light-receiving semiconductor element 4, which islocated opposite to the semiconductor element 1, is die-bonded to thelead frame 5, and then the semiconductor element 4 and another separatelead frame 5 (which is not shown in FIG. 1) are wire-bonded with the useof a bonding wire 6 made of gold. After filling the space between thesemiconductor elements with the curable organopolysiloxane compositionof the invention, the composition is cured by heating at 50° C. to 200°C. The semiconductor elements embedded in the transparent cured body 7of the aforementioned curable organopolysiloxane composition are thensealed in a white epoxy resin cover 8.

On the other hand, a LED of the type shown in FIG. 2 contains asemiconductor element 9, which is die-bonded to a lead frame 10 andwire-bonded to a lead frame 11 by a bonding wire 12. The aforementionedsemiconductor element 9 is coated with a cured body 13 of the curableorganopolysiloxane composition of the invention which contains 5 to 15wt. % of a luminescent substance (YAG). The semiconductor element 9coated with the cured body 13 is, in turn, sealed by embedding in atransparent sealing resin 14, in particular in an cured body of acurable organopolysiloxane composition of the invention, but without aluminescent substance.

In the production of the LED shown in FIG. 2, the semiconductor element9 is die-bonded to the lead frame 10, and then the semiconductor element9 is wire-bonded to a lead frame 11 with the use of a bonding wire 12made of gold. The semiconductor element 9 is then coated with thecurable organopolysiloxane composition of the invention that contains 5to 15 wt. % of a luminescent substance (YAG), and the composition iscured by heating at 50° C. to 200° C. The semiconductor element 9 coatedwith the cured body 13 of the aforementioned curable organopolysiloxanecomposition is then sealed in a curable organopolysiloxane compositionof the invention, but without a luminescent substance.

EXAMPLES

The curable organopolysiloxane composition and the semiconductorelements of the invention will be further described in more detail withreference to practical examples. Values of viscosity used in thepractical examples were measured at 25° C. Characteristics of thecurable organopolysiloxane composition and of the semiconductor elementswere measured by the methods described below.

Hardness of the Cured Body

The cured body was obtained by heating the curable organopolysiloxanecomposition for 1 hour at 150° C. in a hot-air-circulation oven. Thehardness of the cured body was measured by means of a Type A durometerspecified by JIS K 6253.

Tensile Strength

A cured body having the shape of a dumbbell-type specimen No. 3according to JIS K 6251 was produced by heating the curableorganopolysiloxane composition for 1 hour at 150° C. in ahot-air-circulation oven. The tensile strength of the cured body wasmeasured with a procedure specified in JIS K 6251.

Resistance to Scratching

The curable organopolysiloxane composition was poured onto an aluminumplate (55 mm diameter) so as to form a 1 mm-thick layer, and the contentof the plate was cured by heating at 150° C. for 1 hour in ahot-air-circulation oven. As a result, a plate-like cured body wasformed. The surface of this plate was scratched 10 times with a nail,and then the degree of the surface damage was evaluated. The followingdesignations were used for evaluation criteria: ◯—no scratches after 10times; Δ—scratches after 2 to 10 times; X—scratch after 1 time.Furthermore, appearance of the sample was observed after 100 hourtreatment at 150° C. in a hot-air-circulation oven.

Index of Refraction through the Curable Organopolysiloxane Compositionand Cured Body

Index of refraction through the curable organopolysiloxane compositionat 25° C. was measured with the Abbe refractometer. Measurements werecarried out with a visible light (589 nm). The curableorganopolysiloxane composition was then cured by heating for 1 hour at150° C. in a hot-air-circulation oven, and the index of refraction at25° C. for the light passing through the obtained cured body wasmeasured in the same manner as for the composition.

Visible Light Permeability through the Curable OrganopolysiloxaneComposition and Cured Body

Visible light permeability through a curable organopolysiloxanecomposition (optical path length 1.0 mm) at 25° C. was measured.Measurements were carried out with visible light with the wavelength of420 nm. The curable organopolysiloxane composition was then cured byheating for 1 hour at 150° C. in a hot-air-circulation oven, andpermeability of light through the cured body at 25° C. (optical pathlength 1.0 mm) was measured.

Ultraviolet Light Permeability through the Curable OrganopolysiloxaneComposition and Cured Body

Permeability of ultraviolet light (with wavelength of 230 nm) through acurable organopolysiloxane composition (optical path length 1.0 mm) at25° C. was measured by means of a spectrophotometer. The curableorganopolysiloxane composition was then cured by heating for 1 hour at150° C. in a hot-air-circulation oven, and permeability of ultravioletlight through the cured body at 25° C. (optical path length 1.0 mm) wasmeasured.

The following procedures were used for evaluating reliability of thesemiconductor device.

Reliability Evaluation Procedure No. 1

The photocoupler shown in FIG. 1 was produced in the following manner. AGa—Al—As type semiconductor element 1 was die-bonded to a lead frame 2by means of a conductive paste. The semiconductor element 1 and anotherlead frame 2 were then wire-bonded to each other with the use of abonding wire 3 made of gold. A light-receiving semiconductor element 4located opposite to the semiconductor element 1 was wire-bonded to alead frame 5 by means of a bonding wire 6 made of gold. The spacebetween the electrodes was filled with the curable organopolysiloxanecomposition, which was then cured for 1 hours at 150° C. in ahot-air-circulation oven. The semiconductor elements coated with a curedbody 7 of the aforementioned composition were then sealed in a whiteepoxy resin 8. Ten photocouplers were produced by the method describedabove. Light-generation power of each photocoupler was measured prior toand after heat treatment during 100 hours at 150° C. in ahot-air-circulation oven, and an average value of the light-generationpower developed by the photocouplers after the heat treatment wascalculated in a ratio relative to the light-generation power prior tothe heat treatment, which was assumed as 100.

Reliability Evaluation Procedure No. 2

The LED shown in FIG. 2 was produced in the following manner. A Ga—Ntype semiconductor element 9 was die-bonded to a lead frame 10 by meansof a conductive paste. The semiconductor element 9 and a lead frame 11were then wire-bonded to each other with the use of a bonding wire 12made of gold. The semiconductor element 9 was coated with the curableorganopolysiloxane composition that contained 10 wt. % of a luminescentsubstance (YAG), and the composition was then cured for 1 hour at 150°C. in a hot-air-circulation oven. The semiconductor element 9 coatedwith a cured body 13 of the aforementioned composition was then sealedin a transparent sealing resin 14 prepared from the sameorganopolysiloxane composition as above but without the luminescentsubstance. Sealing was carried out by heating for 1 hour at 150° C. in ahot-air-circulation oven. Ten such LED's were produced by the methoddescribed above. Light-emitting power of each LED was measured prior toand after heat treatment of the LED during 100 hours at 150° C. in ahot-air-circulation oven, and an average value of the light-generationpower developed by the LED after the heat treatment was calculated in aratio relative to the light-generation power prior to the heat treatmentwhich was assumed as 100.

Practical Example 1

A 3,250 mPa·s viscosity, curable organopolysiloxane composition wasprepared by uniformly mixing:

45 parts by weight of 3,500 mPa·s viscosity, straight-chainmethylphenylpolysiloxane having both molecular terminals capped withdimethylvinylsiloxy groups with 0.20 wt. % content of silicon-bondedvinyl groups and 49 mole % of silicon-bonded phenyl groups among allsilicon-bonded organic groups,

20 parts by weight of a branched-chain organopolysiloxane having thefollowing average unit formula:(C₆H₅SiO_(3/2))_(0.75)[(CH₂═CH)(CH₃)₂ SiO_(1/2)]_(0.25)having a solid state at 25° C., containing 20 mole % of silicon-bondedvinyl groups and 50 mole % of silicon-bonded phenyl groups of all thesilicon-bonded organic groups, and having a weight-average molecularweight referenced to polystyrene of 1,600,

30 parts by weight of a 950 mPa·s branch-chain organopolysiloxane havingthe following average unit formula:(C₆H₅SiO_(3/2))_(0.60)[(CH₃)₂HSiO_(1/2)]_(0.40)containing 20 mole % of silicon-bonded hydrogen atoms and 33 mole % ofsilicon-bonded phenyl groups among all silicon-bonded groups, having aweight-average molecular weight referenced to polystyrene of 1,100 andwhere the amount of silicon-bonded hydrogen atoms was 1.3 moles per 1mole of the silicon-bonded vinyl groups contained in the aforementionedmethylphenylpolysiloxane and the branch-chain organopolysiloxane,

a complex of platinum with 1,3-divinyl-1,1,3,3-tetramethyldisiloxane insuch an amount that in weight units metallic platinum comprised 2.5 ppm,and

0.05 parts by weight of 2-phenyl-3-butyn-2-ol.

Characteristics of the curable organopolysiloxane composition and of thecured body were measured. The results of measurement are presented inTable 1. Furthermore, a photocoupler and LED were manufactured with theuse of the aforementioned organopolysiloxane composition. Table 1 alsocontains results of evaluating reliability of the obtainedsemiconductors.

Comparative Example 1

A 4,500 mPa·s viscosity, curable organopolysiloxane composition wasprepared by uniformly mixing:

75 parts by weight of 3,500 mPa·s viscosity, straight-chainmethylphenylpolysiloxane having both molecular terminals capped withdimethylvinylsiloxy groups containing 0.20 wt. % content ofsilicon-bonded vinyl groups and 49 mole % of silicon-bonded phenylgroups among all silicon-bonded organic groups,

17 parts by weight of a 950 mPa·s viscosity, branched-chainorganopolysiloxane having the following average unit formula:(C₆H₅SiO_(3/2))_(0.60)[(CH₃)₂HSiO_(1/2)]_(0.40)containing 20 mole % of silicon-bonded hydrogen atoms and 33 mole % ofsilicon-bonded phenyl groups among all silicon-bonded groups, having aweight-average molecular weight referenced to polystyrene of 1,100,where the amount of silicon-bonded hydrogen atoms was 1.3 moles per 1mole of the silicon-bonded vinyl groups contained in the aforementionedmethylphenylpolysiloxane,

a complex of platinum with 1,3-divinyl-1,1,3,3-tetramethyldisiloxane insuch an amount that in weight units metallic platinum comprised 2.5 ppm,and

0.05 parts by weight of 2-phenyl-3-butyn-2-ol.

Characteristics of the curable organopolysiloxane composition and of thecured body were measured. The results of measurement are presented inTable 1. Furthermore, a photocoupler and LED were manufactured with theuse of the aforementioned organopolysiloxane composition. Table 1 alsocontains results of evaluating reliability of the obtainedsemiconductors.

Comparative Example 2

A 2,000 mPa·s viscosity, curable organopolysiloxane composition wasprepared by uniformly mixing

52 parts by weight of a branch-chain organopolysiloxane having thefollowing average unit formula:(C₆H₅SiO_(3/2))_(0.75)[(CH₂═CH)(CH₃)₂ SiO_(1/2)]_(0.25)having a solid state at 25° C., containing 20 mole % of silicon-bondedvinyl groups and 50 mole % of silicon-bonded phenyl groups of all thesilicon-bonded organic groups, and having a weight-average molecularweight referenced to polystyrene of 1,600,

43 parts by weight of a 950 mPa·s viscosity, branch-chainorganopolysiloxane having the following average unit formula:(C₆H₅SiO_(3/2))_(0.60) [(CH₃)₂HSiOi/₂]_(0.40)containing 20 mole % of silicon-bonded hydrogen atoms and 33 mole % ofsilicon-bonded phenyl groups among all silicon-bonded groups, having aweight-average molecular weight referenced to polystyrene of 1,100, andwhere the amount of silicon-bonded hydrogen atoms was 1.3 moles per 1mole of the silicon-bonded vinyl groups contained in the aforementionedbranch-chain organopolysiloxane,

a complex of platinum with 1,3-divinyl-1,1,3,3-tetramethyldisiloxane insuch an amount that in weight units metallic platinum comprised 2.5 ppm,and

0.05 parts by weight of 2-phenyl-3-butyn-2-ol.

Characteristics of the curable organopolysiloxane composition and of thecured body were measured. The results of measurement are presented inTable 1. Furthermore, a photocoupler and LED were manufactured with theuse of the aforementioned organopolysiloxane composition. Table 1 alsocontains results of evaluating reliability of the obtainedsemiconductors.

Practical Example 2

A 3,500 mPa·s viscosity, curable organopolysiloxane composition wasprepared by uniformly mixing

61.5 parts by weight of 3,500 mPa·s viscosity, straight-chainmethylphenylpolysiloxane having both molecular terminals capped withdimethylvinylsiloxy groups (with 0.20 wt. % content of silicon-bondedvinyl groups and 49 mole % of silicon-bonded phenyl groups),

20.3 parts by weight of a branched-chain organopolysiloxane having thefollowing average unit formula:(C₆H₅SiO_(3/2))_(0.75)[(CH₂═CH)(CH₃)₂SiO_(1/2]) _(0.25)having a solid state at 25° C., and containing 20 mole % ofsilicon-bonded vinyl groups and 50 mole % of silicon-bonded phenylgroups among all silicon-bonded organic groups, and having aweight-average molecular weight referenced to polystyrene of 1,600),

12.8 parts by weight of a 20 mPa·s branch-chain organopolysiloxanehaving the following average unit formula:(SiO_(4/2))_(0.60)[(CH₃)₂HSiO_(1/2)]_(0.40)containing 33 mole % of silicon-bonded hydrogen atoms among allsilicon-bonded groups, such that the amount of silicon-bonded hydrogenatoms was 1.3 moles per 1 mole of the silicon-bonded vinyl groupscontained in the aforementioned methylphenylpolysiloxane and thebranch-chain organopolysiloxane,

a complex of platinum with 1,3-divinyl-1,1,3,3-tetramethyldisiloxane insuch an amount that in weight units metallic platinum comprised 2.5 ppm,and

0.05 parts by weight of 2-phenyl-3-butyn-2-ol.

Characteristics of the curable organopolysiloxane composition and of thecured body were measured. The results of measurement are presented inTable 1. Furthermore, a photocoupler and LED were manufactured with theuse of the aforementioned organopolysiloxane composition. Table 1 alsocontains results of evaluating reliability of the obtainedsemiconductors. TABLE 1 Examples Practical Comparative Examples ExamplesCharacteristics 1 2 1 2 Curable Organopolysiloxane Index of Refraction1.54 1.53 1.54  1.54 Light permeability (%) 100 31 100 100 Cured BodyHardness 65 70 45  95 Tensile Strength (Mpa) 1.8 0.8 0.23  0.11Resistance to Scratching ◯ ◯ X ◯ Index of Refraction 1.54 1.53 1.54 1.54 Light permeability (%) 100 85 97  92 UV Light permeability (%) 0 00  0 Reliability of Semiconductor Evaluation Method No. 1 RelativeLight-Generation 100 100 84  45* Power (%) Evaluation Method No. 2Relative Light-Generation 100 100 72  43* Power (%)*Surface cracks developed on all specimens after 100 hours of heattreatment at 150° C.

INDUSTRIAL APPLICABILITY

The curable organopolysiloxane composition of the invention ischaracterized by high coefficient of refraction, permeability of light,and mechanical strength. A cured body of the composition ischaracterized by good resistance to scratching. Furthermore, as thesemiconductor devices of the invention are covered with a cured body ofthe aforementioned composition, they have excellent reliability.

1. A curable organopolysiloxane composition comprising: (A) astraight-chain organopolysiloxane having per molecule at least twosilicon-bonded alkenyl groups and at least one silicon-bonded arylgroup; (B) a branched-chain organopolysiloxane with siloxane unitsrepresented by the general formula:RSiO_(3/2) where R is a substituted or unsubstituted monovalenthydrocarbon group, and where component (B) has per molecule, at leastone silicon-bonded alkenyl group and at least one silicon-bonded arylgroup, and where component (B) is used in a weight ratio of 1/99 to 99/1based on the weight of component (A); (C) an organopolysiloxane havingper molecule at least two silicon-bonded hydrogen atoms, where component(C) is used in an amount of 1 to 200 parts by weight for each 100 partsby weight of the total weight of parts (A) and (B); and (D) ahydrosilylation catalyst in an amount sufficient to promote curing ofthe composition.
 2. The curable organopolysiloxane composition of claim1, where component (A) has a content of silicon-bonded aryl groups notless than 40 mole % of all silicon-bonded organic groups in component(A).
 3. The curable organopolysiloxane composition of claim 1, wherecomponent (A) is an organopolysiloxane represented by the generalformula:

where each R¹ comprises the same or different substituted orunsubstituted monovalent hydrocarbon groups, at least two R¹'s comprisealkenyl groups, at least one R¹ comprises an aryl group, and n is aninteger from 5 to
 1000. 4. The curable organopolysiloxane composition ofclaim 1, where component (B) has average unit formula:(R²SiO_(3/2))_(a)(R² ₂SiO_(2/2))_(b)(R²₃SiO_(1/2))_(c)(SiO_(4/2))_(d)(XO_(1/2))_(e) where each R² is the sameor different substituted or unsubstituted monovalent hydrocarbon group,0.1 to 40 mole % of all R²'s are alkenyl groups, more than 10 mole % ofall R²'s are aryl groups, X is a hydrogen atom or an alkyl group, a is apositive number, b is 0 or a positive number, c is 0 or a positivenumber, d is 0 or a positive number, e is 0 or a positive number, b/a is0 to 10, c/a is 0 to 0.5, d/(a+b+c+d) is 0 to 0.3, and e/(a+b+c+d) is 0to 0.4.
 5. The curable organopolysiloxane composition of claim 1, whereall or a portion of component (C) has average unit formula:(R³SiO_(3/2))_(f)(R³ ₂SiO_(2/2))_(g)(R³ ₃SiO_(1/2))_(h)(SiO_(4/2))_(i)(X′O_(1/2))_(j) where each R³ is the sameor different alkenyl groups, substituted or unsubstituted monovalenthydrocarbon groups, or hydrogen atoms; 0.1 to 40 mole % of all R³'s arehydrogen atoms; more than 10 mole % of all R³'s are aryl groups; X′ is ahydrogen atom or an alkyl group, f is a positive number, g is 0 or apositive number, h is 0 or a positive number, i is 0 or a positivenumber, j is 0 or a positive number, g/f is 0 to 10, h/f is 0 to 0.5,i/(f+g+h+i) is 0 to 0.3, and j/(+g+h+i) is 0 to 0.4.
 6. The curableorganopolysiloxane composition of claim 1, where an index of refractionat 25° C. for visible light having a wavelength of 589 nm passingthrough an object obtained by curing the curable organopolysiloxanecomposition of claim 1 is equal to or exceeds 1.5.
 7. The curableorganopolysiloxane composition of claim 1, where light permeability at25° C. for visible light passing through an object obtained by curingthe curable organopolysiloxane composition of claim 1 is equal to orexceeds 80%.
 8. A semiconductor device coated with a cured coating madefrom the curable organopolysiloxane according to claim
 1. 9. Thesemiconductor device of claim 8, where said semiconductor devicecomprises a light-emitting element.